Dear all,

since a few weeks, we have been noticing the following 'stuff' swimming in our flasks (see images attached). The cells we use are self-isolated primary human keratinocytes. They are definitely not any contamination I have seen before. When I think back to the times I have microscoped yeast and fungi, I remember seeing budding cells, spores in phase contrast and ling filamentous structures made up of multiple cells, which I cannot seem to identify here. Does anyone know what this might be (maybe this may be a fungus I have not encountered till now? :-)) and can give us some tips on how to move further based on previous experience? We have already cleaned our cell culture rooms, incubators, hoods, and water baths multiple times with alcohol-based disinfectants and even bleach, but this 'contamination' just keeps coming back.

Thanks in advance for your advice